registry hack which will allow you to see your opponents' cards

Launch REGEDIT.EXE and navigate to HKEY_CURRENT_USER Software Microsoft Windows CurrentVersion Applets Hearts.

NOTE: You may have to create the Hearts key under Applets

In the right-hand pane, create a new String Value. Immediately rename it to "ZB" (without the quotes); give it a value of "42" (again, sans quotes).

The next time you're in a game of Hearts, press CTRL + SHIFT + ALT + F12.